Process for production of polylactic acid resin composition

Abstract

A method for producing a polylactic acid resin composition, including the following steps (1) and (2): step (1): subjecting an organic crystal nucleating agent to a wet pulverization in the presence of a carboxylic acid ester having a weight-average molecular weight of from 150 to 600 and a viscosity at 23° C. of from 1 to 500 mPa·s and/or a phosphoric ester having a weight-average molecular weight of from 150 to 600 and a viscosity at 23° C. of from 1 to 500 mPa·s to give a finely pulverized organic crystal nucleating agent composition; and step (2): melt-kneading a raw material for a polylactic acid resin composition comprising the finely pulverized organic crystal nucleating agent composition obtained in the step (1) and a polylactic acid resin.

The invention claimed is: 
     
       1. A method for producing a polylactic acid resin composition, comprising the following steps (1) and (2):
 step (1): subjecting an organic crystal nucleating agent to a wet pulverization in the presence of a phosphoric ester having a weight-average molecular weight of from 150 to 600 and a viscosity at 23° C. of from 1 to 500 mPa·s to give a finely pulverized organic crystal nucleating agent composition; and 
 step (2): melt-kneading a raw material for a polylactic acid resin composition comprising the finely pulverized organic crystal nucleating agent composition obtained in the step (1) and a polylactic acid resin. 
 
     
     
       2. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the organic crystal nucleating agent comprises at least one organic compound selected from the group consisting of metal salts of dialkyl aromatic sulfonates, metal salts of phosphoric esters, metal salts of phenylphosphonic acids, metal salts of rosin acids, aromatic carboxylic acid amides, and rosin acid amides. 
     
     
       3. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the organic crystal nucleating agent comprises a metal salt of a phenylphosphonic acid. 
     
     
       4. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the finely pulverized organic crystal nucleating agent composition has a volume-median particle size (D 50 ) of from 50 to 700 nm. 
     
     
       5. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the step (1) comprises subjecting the organic crystal nucleating agent to a wet pulverization in the presence of the phosphoric ester, within a range satisfying a ratio of the weight of the organic crystal nucleating agent and a total weight of the phosphoric ester, that is the organic crystal nucleating agent/the phosphoric ester, of from 1/99 to 50/50. 
     
     
       6. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the phosphoric ester comprises a compound represented by the formula (I): 
       
         
           
           
               
               
           
         
         wherein each of R 1 , R 2 , and R 3  is independently an alkyl group having from 1 to 4 carbon atoms; each of A 1 , A 2 , and A 3  is independently an alkylene group having 2 or 3 carbon atoms; each of m, n, and p is independently a positive number representing an average number of moles added for the oxyalkylene group, wherein m+n+p is a number that exceeds 3 and is equal to or less than 12. 
       
     
     
       7. The method for producing a polylactic acid resin composition according to  claim 6 , wherein m+n+p in the formula (I) is a number that exceeds 4 and is less than 12. 
     
     
       8. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the phosphoric ester is one or more members selected from the group consisting of tris(ethoxyethoxyethyl)phosphate, tris(methoxyethoxyethyl)phosphate, tris(propoxyethoxyethyl)phosphate, tris(butoxyethoxyethyl)phosphate, tris(methoxyethoxyethoxyethyl)phosphate, tris(ethoxyethoxyethoxyethyl)phosphate, bis(ethoxyethoxyethyl)methoxyethoxyethoxyethyl phosphate and bis(methoxyethoxyethoxyethyl)ethoxyethoxyethyl phosphate. 
     
     
       9. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the organic crystal nucleating agent subjected to the wet pulverization has a volume-median particle size (D 50 ) of from 500 nm to 5 μm. 
     
     
       10. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the treatment temperature for the wet pulverization is from 5° to 250° C. 
     
     
       11. The method for producing a polylactic acid resin composition according to  claim 1 , wherein the organic crystal nucleating agent is wet pulverized in step (1) with a media pulverizer. 
     
     
       12. The method for producing a polylactic acid resin composition according to  claim 1 , wherein in the step (2) the finely pulverized organic crystal nucleating agent composition obtained in the step (1) is contained in an amount of from 1 to 50 parts by weight, based on 100 parts by weight of the polylactic acid resin.